Soft polyurethane foam and seat pad

Abstract

The present invention provides a soft polyurethane foam which is obtained by expansion molding a starting foam liquid that contains a polyol, a polyisocyanate, a crosslinking agent, a foaming agent and a catalyst. This soft polyurethane foam is configured such that: a polyether polyol having a weight-average molecular weight (Mw) of 3,000 to 12,000 and 3.5 to 4 functional groups is contained therein as the polyol; the value of (ethylene oxide groups)/(propylene oxide groups) (in terms of a molar ratio) in all compounds contained therein as the crosslinking agent is 100 or more; a short-chain polyol having a weight-average molecular weight of 1,000 or less is contained therein as the crosslinking agent; and tolylene diisocyanate is contained therein as the polyisocyanate in an isocyanate index of 70 or more.

1 . A soft polyurethane foam obtained by expansion molding a starting foam liquid which contains a polyol, a polyisocyanate, a crosslinking agent, a foaming agent, and a catalyst,
 wherein a polyether polyol having a weight-average molecular weight Mw of 3,000 to 12,000 and 3 to 4 functional groups is contained as the polyol,   an ethylene oxide group/propylene oxide group (molar ratio) in all compounds included therein as the crosslinking agent is 100 or more,   a short chain polyol having a weight-average molecular weight of 1,000 or less is contained as the crosslinking agent, and   tolylene diisocyanate is contained therein as the polyisocyanate in an isocyanate index of 70 or more.   
     
     
         2 . The soft polyurethane foam according to  claim 1 ,
 wherein at least a gelling catalyst is contained out of a gelling catalyst and a blowing catalyst as the catalyst, and   a mass ratio of the gelling catalyst:the blowing catalyst is 100:0 to 100:100.   
     
     
         3 . The soft polyurethane foam according to  claim 1 ,
 wherein 0.1 to 1.0 part by mass of alkanolamine is contained with respect to 100 parts by mass of the polyol in the starting foam liquid.   
     
     
         4 . The soft polyurethane foam according to  claim 1 ,
 wherein the polyether polyol included in the starting foam liquid is one type and the polyether polyol has 3.5 or more functional groups.   
     
     
         5 . The soft polyurethane foam according to  claim 1 ,
 wherein a polymer polyol is contained as the polyol.   
     
     
         6 . The soft polyurethane foam according to  claim 1 ,
 wherein a rigidity distribution in a thickness direction of the soft polyurethane foam exhibits a continuous increasing trend or decreasing trend.   
     
     
         7 . The soft polyurethane foam according to  claim 1 ,
 wherein, in a rigidity distribution in a thickness direction of the soft polyurethane foam, there is a region exhibiting a substantially constant trend and a region exhibiting a continuous increasing trend or decreasing trend.   
     
     
         8 . A seat pad using the soft polyurethane foam according to  claim 1 .